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• WinForms prints to default printer even if it's not available/connected

  - by Valentein

  How can I determine if printer is connected? Typically this application prints to the default printer but in some cases that printer may not be available. If so I don't want the job sent to it's queue but rather printed to another available printer. I understand the PinterSettings.InstalledPrinters property. Does PrintDocument.PrinterSettings.IsValid return false if a printer is not available? Does WPF provide this kind of functionality? My problem is different than Printing problem in C# windows app - Always prints to default printer

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• Throw exception from initializer list

  - by aaa

  hello. what is the best way to throw exception from initializer list? for example: class C { T0 t0; // can be either valid or invalid, but does not throw directly T1 t1; // heavy object, do not construct if t0 is invalid, by throwing before C(int n) : t0(n), // throw exception if t0(n) is not valid t1() {} }; I thought maybe making wrapper, e.g. t0(throw_if_invalid(n)). What is the practice to handle such cases? Thanks

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• Event Capturing vs Event Bubbling

  - by Rajat

  I just wanted to get the general consensus on which is a better mode of event delegation in JS between bubbling and capturing. Now I understand that depending on a particular use-case, one might want to use capturing phase over bubbling or vice versa but I want to understand what delegation mode is preferred for most general cases and why (to me it seems bubbling mode). Or to put it in other words, is there a reason behind W3C addEventListener implementation to favor the bubbling mode. [capturing is initiated only when you specify the 3rd parameter and its true. However, you can forget that 3rd param and bubbling mode is kicked in] I looked up the JQuery's bind function to get an answer to my question and it seems it doesn't even support events in capture phase (it seems to me because of IE not support capturing mode). So looks like bubbling mode is the default choice but why?

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• Efficient algorithm for finding largest eigenpair of small general complex matrix

  - by mklassen

  I am looking for an efficient algorithm to find the largest eigenpair of a small, general (non-square, non-sparse, non-symmetric), complex matrix, A, of size m x n. By small I mean m and n is typically between 4 and 64 and usually around 16, but with m not equal to n. This problem is straight forward to solve with the general LAPACK SVD algorithms, i.e. gesvd or gesdd. However, as I am solving millions of these problems and only require the largest eigenpair, I am looking for a more efficient algorithm. Additionally, in my application the eigenvectors will generally be similar for all cases. This lead me to investigate Arnoldi iteration based methods, but I have neither found a good library nor algorithm that applies to my small general complex matrix. Is there an appropriate algorithm and/or library?

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• Using YQL multi-query & XPath to parse HTML, how to escape nested quotes?

  - by Tivac

  The title is more complicated than it has to be, here's the problem query. SELECT * FROM query.multi WHERE queries=" SELECT * FROM html WHERE url='http://www.stumbleupon.com/url/http://www.guildwars2.com' AND xpath='//li[@class=\"listLi\"]/div[@class=\"views\"]/a/span'; SELECT * FROM xml WHERE url='http://services.digg.com/1.0/endpoint?method=story.getAll&link=http://www.guildwars2.com'; SELECT * FROM json WHERE url='http://api.tweetmeme.com/url_info.json?url=http://www.guildwars2.com'; SELECT * FROM xml WHERE url='http://api.facebook.com/restserver.php?method=links.getStats&urls=http://www.guildwars2.com'; SELECT * FROM json WHERE url='http://www.reddit.com/button_info.json?url=http://www.guildwars2.com'" Specifically this line, xpath='//li[@class=\"listLi\"]/div[@class=\"views\"]/a/span' It's problematic because of the quoting, I have to nest them three levels deep and I've run out of quote characters to use. I've tried the following variations without success: //no attribute quoting xpath='//li[@class=listLi]/div[@class=views]/a/span' //try to quote attribute w/ backslash & single quote xpath='//li[@class=\'listLi\']/div[@class=\'views\']/a/span' //try to quote attribute w/ backslash & double quote xpath='//li[@class=\"listLi\"]/div[@class=\"views\"]/a/span' //try to quote attribute with double single quotes, like SQL xpath='//li[@class=''listLi'']/div[@class=''views'']/a/span' //try to quote attribute with double double quotes, like SQL xpath='//li[@class=""listLi""]/div[@class=""views""]/a/span' //try to quote attribute with quote entities xpath='//li[@class=&quot;listLi&quot;]/div[@class=&quot;views&quot;]/a/span' //try to surround XPath with backslash & double quote xpath=\"//li[@class='listLi']/div[@class='views']/a/span\" //try to surround XPath with double double quote xpath=""//li[@class='listLi']/div[@class='views']/a/span"" All without success. I don't see much out there about escaping XPath strings but everything I've found seems to be variations on using concat (which won't help because neither ' nor " are available) or html entities. Not using quotes for the attributes doesn't throw an error but fails because it's not the actual XPath string I need. I don't see anything in the YQL docs about how to handle escaping. I'm aware of how edge-casey this is but was hoping they'd have some sort of escaping guide.

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• Problems with matching emails with regex

  - by Gandalf StormCrow

  Hello, I'm trying to match an email address here is what I've come up with so far : String text = "[email protected]"; String regex = "(\\w+)@{1}(\\w+){2,}\\.{1}\\w{2,4}"; This however works with following cases : [email protected] [email protected] [email protected] So it matches any alphanumeric character repeated once or more that comes before one @ followed by any alphanumeric character repeated at least two times(which is minimal characters for any domain name) followed by one .(dot) and followed by any alphanumeric character repeated at least 2 times and at most 4 times(because there are domains such as .us or .mobi). This expression however does not work with emails such as : [email protected] [email protected] [email protected] [email protected] etc as many subdomains or [email protected] [email protected] [email protected] [email protected] I've just started to learn regex and I found interesting to try to solve problems such as these by using regex .. not partially but for each case, any help would be much appriciated. Thank you

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• Main pricing and support for individual client pricing (Database Architecture ideas help - Rails)

  - by slythic

  Hi all, I have a personal project I'm planning and I came to a small hurdle. I want to have an item with price that will be the default for all clients/users. However, in my business I have some clients that are grandfathered in to some special pricing. In the case of these grandfathered in cases, I'll manually plug their special price in my admin section. Then all they will see is their special pricing while the regular users/clients see the default price. What is the best and simplest way to design the back-end for this? FYI - I'll be using rails as my framework. Many thanks! -Tony

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• Any working tutorials for Authlogic?

  - by Mark Wilbur

  I've been trying to build my first rails app and have gotten stuck on the issue of user authentication. I've found a number of tutorials for using various plug-ins to do this, but so far every single one of them is out-dated, and as a result, broken! From what I've read, I think Authlogic may be the best fit for me, and I've tried two things: 1) Going through Railscast, episode #160 (which is a tutorial for setting it up) 2) Using Ryan B's nifty_authentication gem with the --authlogic tag In both cases, I get the following error as soon as I try to do anything with a user: undefined local variable or method `acts_as_authentic' for # I believe this is from the User model: class User < ActiveRecord::Base acts_as_authentic end I'm sure I've installed the authlogic gem, and I've added config.gem "authlogic" to my environment.rb Any ideas about what's wrong? Anybody know of a complete and up to date tutorial for adding user authentication?

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• Why does Silverlight 4 Tools only give partial intellisense?

  - by Edward Tanguay

  I finally got Silverlight 4 Toolkit installed , referenced and working after the difficulty of finding the right namespace described in this question. But intellisense doesn't work fully: after I type "tk:", it doesn't pop up the various controls I have available, but if I type a control name out, e.g. DockPanel, then it works, as shown below. It will even give me intellisense after I type tk:DropPanel, which is odd. How can I get intellisense to work in all cases for the Silverlight 4 Toolkit? I can imagine I need another namespace, but this site says that this reference: is now all you need (and will be automatically used by both Visual Studio and Blend)

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• Main pricing and support for custom client pricing (Database Architecture ideas help - Rails)

  - by slythic

  Hi all, I have a personal project I'm planning and I came to a small hurdle. I want to have an item with price that will be the default for all clients/users. However, in my business I have some clients that are grandfathered in to some special pricing. In the case of these grandfathered in cases, I'll manually plug their special price in my admin section. Then all they will see is their special pricing while the regular users/clients see the default price. What is the best and simplest way to design the back-end for this? FYI - I'll be using rails as my framework. Many thanks! -Tony

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• XML: What to use as a list separator

  - by Heinzi

  There are two ways to specify lists of values in XML. Variant 1: <Database Name="myDatabase"> <Table Name="myTable1" /> <Table Name="myTable2" /> <Table Name="myTable3" /> ... </Database> Variant 2: <Database Name="myDatabase" Tables="myTable1 myTable2 myTable3 ..." /> Clearly, Variant 1 is cleaner and can be extended more easily, but im many cases Variant 2 is more readable and "user-friendly". When using Variant 2, what should be used as the separator? The XML Schema standard seems to prefer whitespace, whereas some real-world examples use commas instead. Is there a particular reason to choose one over the other (assuming that the values contain neither whitspace nor commas)?

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• When we should use pushScene and replaceScene in cocos2d ?

  - by srikanth rongali

  Hi, I cocos2d, I am using pushScene and replaceScene to move to next scene. But, I am confused which we should use? When I am using replaceScene in some places app is crashing and giving errors like -[UITextView length]: unrecognized selector sent to instance 0x842a750 Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[UITextView length]: unrecognized selector sent to instance 0x842a750' But, in my program I am not passing length to UITextView. My program is in this way In scene1 I have UITextView, and I am replacing this scene with scene2. Then -(id)buttonPressed:(id)sender { [description removeFromSuperview]; // It is the textView(description) CCScene *Scene = [CCScene node]; CCLayer *Layer = [scene2 node]; [Scene addChild:Layer]; [[CCDirector sharedDirector] setAnimationInterval:1.0/60]; [[CCDirector sharedDirector] replaceScene: Scene]; } But, when I am using pushScene in presence of replaceScene it is working good. Please clarify me which one should use in which cases ? Thank You

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• How to geocoding big number of addresses?

  - by user308569

  I need to geocode, i.e. translate street address to latitude,longitude for ~8,000 street addresses. I am using both Yahoo and Google geocoding engines at http://www.gpsvisualizer.com/geocoder/, and found out that for a big number of addresses those engines (one of them or both) either could not perform geocoding (i.e.return latitude=0,longitude=0), or return wrong coordinates (incl. cases when Yahoo and Google give different results). What is the best way to handle this problem? Which engine is (usually) more accurate? I would appreciate any thoughts, suggestions, ideas from people who had previous experience with this kind of task.

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• A definitive guide to Url Encoding in ASP .NET

  - by cbp

  I am starting to realise that there are about a bazillion different methods for encoding urls in .NET. I keep finding new ones. They all work slightly differently, but they all have essentially the same summary comments. Does anyone have a definitive matrix that shows the exact differences between the following methods: HttpUtility.UrlEncode HttpUtility.UrlPathEncode Server.UrlEncode Uri.EscapeUriString Uri.EscapeDataString ... are they any more? Also it would be good to match these up with use-cases e.g.: Urls in href attributes of a tags Urls to be displayed to the user in HTML Urls as querystring values (i.e. to be sent in GET requests) Urls to be sent in POST requests etc

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• ASP.NET MVC Model Binding

  - by Noel

  If i have a Controller Action that may recieve both HTTP GET and HTTP POST from a number of different sources with each source sending different data e.g. Source1 performs a form POST with two form items Item1 and Item2 Source2 performs a GET where the data is contained in the query string (?ItemX=2&ItemY=3) Is it possible to have a controller action that will cater for all these cases and perform binding automatically e.g. public ActionResult Test(Dictionary data) { // Do work ... return View(); } Is this possible with a custom binder or some other way? Dont want to work directly with HttpContext.Request if possible

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• Call a protected method from outside a class in PHP

  - by Chad Johnson

  I have a very special case in which I need to call a protected method from outside a class. I am very conscious about what I do programmingwise, but I would not be entirely opposed to doing so in this one special case I have. In all other cases, I need to continue disallowing access to the internal method, and so I would like to keep the method protected. What are some elegant ways to access a protected method outside of a class? So far, I've found this. I suppose it may be possible create some kind of double-agent instance of the target class that would sneakily provide access to the internals...

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• Building big, immutable objects without constructors having long parameter lists

  - by Malax

  Hi StackOverflow! I have some big (more than 3 fields) Objects which can and should be immutable. Every time I run into that case i tend to create constructor abominations with long parameter lists. It doesn't feel right, is hard to use and readability suffers. It is even worse if the fields are some sort of collection type like lists. A simple addSibling(S s) would ease the object creation so much but renders the object mutable. What do you guys use in such cases? I'm on Scala and Java, but i think the problem is language agnostic as long as the language is object oriented. Solutions I can think of: "Constructor abominations with long parameter lists" The Builder Pattern Thanks for your input!

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• Dns.GetHostEntry returns multiple IP addresses

  - by spender

  This question probably highlights a lack of understanding of networking principals on my part, rather than a programming issue. I'm doing a lookup on a hostname using Dns.GetHostEntry This returns an IPHostEntry to me, which has an AddressList property which is an array of IPAddress. I always thought there is a 1 to 1 mapping between hostname and IP, but I'm finding that in some cases I get back several IPAddress(es) for the same host. This is a surprise to me. Which part of domain name resolution do I not understand?

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• QT- QImage and multi-threading problem.

  - by umanga

  Greetings all, Please refer to image at : http://i48.tinypic.com/316qb78.jpg We are developing an application to extract cell edges from MRC images from electron microscope. MRC file format stores volumetric pixel data (http://en.wikipedia.org/wiki/Voxel) and we simply use 3D char array(char***) to load and store data (gray scale values) from a MRC file. As shown in the image,there are 3 viewers to display XY,YZ and ZX planes respectively. Scrollbars on the top of the viewers use to change the image slice along an axis. Here is the steps we do when user changes the scrollbar position. 1) get the new scrollbar value.(this is the selected slice) 2) for the relavant plane (YZ,XY or ZX), generate (char* slice;) array for the selected slice by reading 3D char array (char***) 3) Create a new QImage* (Format_RGB888) and set pixel values by reading 'slice' (using img-setPixel(x,y,c);) 4) This new QImage* is painted in the paintEvent() method. We are going to execute "edge-detection" process in a seperate thread since it is an intensive process.During this process we need to draw detected curve (set of pixels) on top of above QImage*.(as a layer).This means we need to call drawPoint() methods outside the QT thread. Is it the best wayto use QImage for this case? What is the best way to execute QT drawing methods from another thread? thanks in advance,

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• How get file names using OpenFileDialog in .NET (1000+ file multiselect)

  - by Cole

  Maybe some of you have come across this before.... I am opening files for parsing. I'm using OpenFileDialog, of course, but i'm limited to a buffer of 2048 on the .FileNames string. Thus, I can only select a few hundred files. This is OK for most cases. However, fore example, I have in one case 1400 files to open. Do you know a way to do this with the open file dialog. I just want the string array of .FileNames, I pass that to parser class. I was also thinking of offering a FolderBrowserDialog option and then I'd use some other method to just loop through all the files in a directory, like the DirectoryInfo class. I'd do this as a last resort if I can't have an all in one solution.

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• Comparing (similar) images with Python/PIL

  - by Attila Oláh

  I'm trying to calculate the similarity (read: Levenshtein distance) of two images, using Python 2.6 and PIL. I plan to use the python-levenshtein library for fast comparison. Main question: What is a good strategy for comparing images? My idea is something like: Convert to RGB (transparent - white) (or maybe convert to monochrome?) Scale up the smaller one to the larger one's size Convert each channel (= the only channel, if converted to monochrome) to a sequence (item value = color value of the pixel) Calculate the Levenshtein distance between the two sequences Of course, this will not handle cases like mirrored images, cropped images, etc. But for basic comparison, this should be useful. Is there a better strategy documented somewhere?

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• When would ShowDialog() return null?

  - by Joe White

  WPF's Window.ShowDialog method returns a nullable boolean. So does CommonDialog.ShowDialog. Now, I understand cases where these would return false (user clicked Cancel or pressed Esc), and when they would return true (code sets Window.DialogResult to true, probably in response to OK being clicked). But null? My first thought is that clicking the title bar's Close button might return null. But the docs state (and I confirmed by testing) that the title-bar Close button is treated as a Cancel. So when would Window.ShowDialog or CommonDialog.ShowDialog ever return null?

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• Cross domain cookie reading/setting cross browsers

  - by Rac123

  I know there are already a few threads available here on this subject but I want others' opinion on this. There are two ways to set/read the cross domain cookies: Creating IFrame on A.com pointing to a page on B.com which creates the cookie and pass that information by creating another IFrame on B.com side pointing to A.com, either using window.name or in location.href.hash A.com page makes a XHR/JSONP call to B.com web service/page that has the following headers and it also sets up the cookie and returns the value. AddHeader("p3p", "CP=\"IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT\"") As we don't have postMessage available across all the browsers, I believe we have to go with one of the cases mentioned above. My question is which is a better way (cleaner) and why to implement for cross browser. Using any other JS framework is out of scope of this discussion. If there's another better way, please mention here! Thank you for your intelligent input in advance! :)

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• Visual studio not detecting that exe is out of date after perforce revert

  - by CHaskell2

  This is a bit of an odd situation. Here's what's happening. So, we have a VS2008 project which outputs to a number of files under perforce control. These files have the always writable flag set. I compile the project in VS, which gives me up to date binaries on my machine. If I then revert those binaries via perforce, I have the version of the binaries that were up on perforce (ie, old ones.) Despite this, compiling the project again at this point detects no changes and will not remake those binaries. In a way, this makes sense, since none of the code or obj files have changed, but it's not really what I want to happen. This comes up in an edge case on our automated build server. I can think of tons of different little hacks I could do to fix this, but I'm thinking I could be missing something fundamental here. The actual build process uses the Unreal build tool, so there is a bit of magic going on behind the scenes that I'm not entirely familiar with too. Edit: This is a C/C++ project, forgot to mention that.

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• Django users and authentication from external source

  - by Boldewyn

  I have a Django app that gets it's data completely from an external source (queried via HTTP). That is, I don't have the option for a local database. Session data is stored in the cache (on my development server I use a SQLite database, so that is no error source). I'm using bleeding edge Django 1.1svn. Enter the problem: I want to use Django's own authentication system for the users. It seems quite simple to write my own Authentication Backend, but always just under the condition that you have a local database where to save the users. Without database my main problem is persistence. I tried it with the following (assume that datasource.get() is a function that returns some kind of dict): class ModelBackend (object): """Login backend.""" def authenticate (self, username=None, password=None): """Check, if a given user/password combination is valid""" data = datasource.get ('login', username, password) if data and data['ok']: return MyUser (username=username) else: raise TypeError return None def get_user (self, username): """get data about a specific user""" try: data = datasource.get ('userdata', username) if data and data['ok']: return data.user except: pass return None class MyUser (User): """Django user who isn't saved in DB""" def save (self): return None But the intentionally missing save() method on MyUser seems to break the session storage of a login. How should MyUser look like without a local database?

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